The Sorrows of Young Werther, or simply Werther, is a 1774 epistolary novel by Johann Wolfgang Goethe, which appeared as a revised edition in 1787. It was one of the main novels in the Sturm und Drang period in German literature, and influenced the later Romantic movement. Goethe, aged 24 at the time, finished Werther in five and a half weeks of intensive writing in January to March 1774. It instantly placed him among the foremost international literary celebrities and was among the best known of his works. The novel is made up of biographical and auto-biographical facts in relation to two triangular relationships and one individual: Goethe, Christian Kestner, and Charlotte Buff ; Goethe, Peter Anton Brentano, Maximiliane von La Roche, and Karl Wilhelm Jerusalem, who died by suicide on the night of Oct 29 or 30, 1772. He shot himself in the head with a pistol borrowed from Kestner. The novel was adapted as the opera Werther by Jules Massenet in 1892.

An epistolary novel is a novel written as a series of letters between the fictional characters of a narrative. The term is often extended to cover novels that intersperse documents of other kinds with the letters, most commonly diary entries and newspaper clippings, and sometimes considered to include novels composed of documents even if they do not include letters at all. More recently, epistolaries may include electronic documents such as recordings and radio, blog posts, and e-mails. The word epistolary is derived from Latin from the Greek word epistolē, meaning a letter (see epistle). This type of fiction is also sometimes known by the German term Briefroman or more generally as epistolary fiction.